1. Field of the Invention
The present invention relates to a radial gap-type motor in which a three-phase winding wound in a distributed winding form is inserted in slots of a stator, and a winding arrangement method therefor.
2. Description of the Related Art
The winding arrangement for a three-phase motor may be largely classified into two types: concentrated winding and distributed winding.
The concentrated winding is such that coils are wound directly in slots and coil ends do not overlap adjacent coils so that it is possible to make small the coil ends.
In contrast, the distributed winding is such that coils for each phase are wound in a distributed manner onto slots. With the distributed winding, the coils for the three phases are inserted in the slots in a manner overlapping each other at the coil ends so that the coil ends become large. Due to the coil ends becoming large, the winding resistance is increased, which results in an increase in the copper loss when a current is caused to flow through the motor. In other words, the output of the motor in response to input power is decreased so that the efficiency of the motor is deteriorated.
Description will be made of a conventional distributed winding method for a three-phase radial gap-type motor hereinbelow. FIG. 9 is a perspective view illustrating blades to be used for distributed winding, and FIG. 10 is a fragmentary sectional view illustrating a positional relationship between blades and a stator core. For distributed winding, blades 51 (rods) are used which have a shape with an outer diameter slightly smaller than the inner diameter of a stator core 52 and a width substantially equal to the tooth tip of teeth 61 of the stator core 52. FIGS. 11 through 14 are views illustrating a conventionally used method of distributed winding for a radial gap-type motor. First, as illustrated in FIG. 11, coils 53, which are molded for each one pole pair, are engaged with the blades 51. When the coils 53 are sequentially engaged with the blades 51 to the extent of being inserted in the slots 55 at a time, a stator core 52 is set beyond the blades 51 with which the coils 53 are engaged as illustrated in FIG. 12, and then by inserting an insert rod 54 formed with projections each having a width substantially equal to that of the slot opening portion and an outer diameter substantially equal to the inner diameter of the stator core 52, the coils 53 are inserted in the slots 55 from the slot opening portion of the stator core 52. FIGS. 13 and 14 are sectional views when FIG. 12 is cut along the circumferential direction; of these views, FIG. 13 illustrates a state on the way of inserting the coil 53 in the slot 55 using the insert rod 54, while FIG. 14 illustrates a state in which the insertion of the coil 53 in the slot 55 is completed.
As a winding arrangement method of distributed winding, there is a method in which the winding for each of the three phases is inserted sequentially. FIG. 15 is a developed sectional view schematically illustrating an example of 8-pole-pair and 36-slot winding arrangement for a conventional distributed winding radial gap-type motor, and FIG. 16 is a cross-sectional view illustrating the 8-pole-pair and 36-slot winding arrangement for the radial gap-type motor illustrated in FIG. 15. In FIGS. 15 and 16, the respective slots S are assigned identification numerals 1 to 36 in column B along the direction of rotation of the motor. Further in FIG. 15, the coils are represented by thick solid lines, the terminals of power source input side lead lines of the respective phases are represented by a “circle”, and the neutral points of the respective phases are represented by a “square”. Further, when the coils for the three phases are wound in the form of a two-layer winding with 8 pole-pairs and 36 slots, it follows that two same phase coils or two different phase coils, with one for each phase, are arranged, but in FIG. 15, for the sake of simplicity of the drawing, the coils for the three phases, which are arranged in the slots, are schematically represented in three rows corresponding to the respective phases. Further in FIG. 16, the representation of the sectional shape, per se, of the coils in the slots S is omitted; the coils of the respective phases in the slots are represented by characters “+U”, “−U”, “+V”, “−V”, “+W”, and “−W”; and only the power source input side lead lines of the respective phases are represented by thick solid lines.
In this winding arrangement method, first for each of the three phases, for example, two large coils of 5-slot pitch and one small coil of 2-slot pitch are formed in a concentric form as one pole pair of coils. Further, at each phase, all the coils, which are molded for each one pole pair, are connected in series. Then, for the coils connected in series for each phase, the coils for U phase are first engaged with the blades, then the coils for V phase are engaged with the blades, and then the coils for W phase are engaged with the blades. Further, the coils are inserted in the stator core while being engaged with the blades. Thus, since it is a simple task that “for each phase, the coils molded for each one pole pair are sequentially engaged with the blades while all being connected in series to each other, and the resultant structure is inserted in the stator core”, there is an advantage that automatic processing of the winding arrangement using a machine is facilitated. However, there is a tendency that at the coil ends the three-phase coils cross (overlap) each other in a complicated manner as illustrated in FIG. 16. Focusing attention on the V phase, for example, indicates that the lead wire from the −U phase coil and the lead wire from the +W phase coil are located between the lead wire from the +V phase coil and the lead wire from the −V phase coil, and the three phase coils are crossing each other. Therefore, the method for sequentially inserting the three-phase coils for each phase has a problem in that the coil ends become large.
The crossing of the coils at the coil ends such as described above can be improved to a certain degree by devising the way of connection between the coils for one coil pair as described hereinafter. FIG. 17 is a developed sectional view schematically illustrating a further example of an 8-pole-pair and 36-slot winding arrangement for the conventional distributed winding radial gap-type motor, and FIG. 18 is a cross-sectional view illustrating of the 8-pole-pair and 36-slot winding arrangement for the radial gap-type motor illustrated in FIG. 17. In FIGS. 17 and 18, the respective slots are assigned identification numbers 1 to 36 in column B along the direction of rotation of the motor. Further, in FIG. 17, the coils are represented by thick solid lines; terminals of power source input side lead lines of the respective phases are represented by “circle”; and the neutral points of the respective phases are represented by “square”. Further, in FIG. 17, the three-phase coils arranged in the slots are represented in two rows for the sake of simplicity of the drawing. Further in FIG. 18, the representation of the sectional shape, per se, of the coils in the slots S is omitted, the coils of the respective phases in the slots are represented by characters “+U”, “−U”, “+V”, “−V”, “+W”, and “−W”, and only the power source input side lead lines of the respective phases are represented by thick solid lines. In order to prevent the coils of the respective phases from crossing each other at the coil ends as illustrated in FIG. 18, the coils wound for each one pole pair are arranged in sequence for each of the three phases as illustrated in FIG. 17, and in addition, the coils between the same phases are connected in series. This provides an advantage in that the coil ends can be made small. However, when priority is given to preventing the coils of each phase from crossing at the coil ends, a state tends to occur in which the coils cross each other in the slots in a complicated manner, as can be seen from FIG. 17, thus complicating the work in which “for each phase, the coils molded for each one pole pair are engaged with the blades while all being connected in series”, so that difficulty is encountered in automatic processing of the winding arrangement using a machine.
Further, as disclosed in Japanese Unexamined Patent Publication No. H4-265645, for example, an invention has been proposed which achieves a reduction of the winding man-hours and a decrease in the winding resistance by reducing the number of layers of unit coil in each slot in a synchronous motor, while maintaining an electric permeability that is equivalent to that of a multilayer winding and distributed winding arrangement.